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Yeasty Business

At the very heart of Vault City Brewing lies our house mixed-culture.

A mysterious, almost mythical entity which gives us so much. Born out of a string of various experiments with yeast and bacteria we've settled on a unique blend of Kveik and Lactobacillus strains which provide us with delicious tropical esters and a deliciously tart acidity.

Let’s start with Kveik. Originally the word was used as a verb meaning "to start" or to "begin life" – a fitting etymology for the backbone of our Modern Sour Beer. This hardy yeast is a (barely) domesticated strain which has been passed down through Norwegian farmhouse brewing using Kveik rings - ceremonial wooden rings which are left in the beer to harbour yeast cells and dried out by the fire to preserve them.

Due to their rather Viking upbringing they are notoriously hardy, and hard working. We allow this yeast to reach an extremely hot fermentation for the juicy, fruity ester profile we’re looking for, though it can ferment at almost freezing temperatures as well!

Now we’ve covered the fruity fermentation we should move on to the bacteria, Lactobacillus to be exact!

This is one type of bacteria known as Lactic Acid Bacteria (LAB) which produces, you guessed it, lactic acid! A cleaner, brighter, more refreshing acid than the likes of acetic (nail polish) or malic (unripe plums) acids. Different species of Lactobacillus are used to ferment yogurt, cheese, sauerkraut, pickles, wine, cider, kimchi.

The lemony, tart, ‘sherbet-y’ character of our base sour beer is down to this versatile bug. Within our house mixed-culture there are several varieties of lactobacillus competing alongside the Kveik yeast and symbiotically creating a wonderful world of flavour. 

Together they are responsible for the delicate, balanced, delicious base of our Modern Sour Beer. All for the price of constantly supplying them with fresh wort… Seems fair!


Andy + Team VC x

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